This invention relates in general to apparatus and processes for fabricating flexible belts.
Various techniques have been devised to form belts from webs. Thermoplastic webs may be joined by overlapping the edge of one web over another and placing the overlapped or seam portion of the webs over a base beneath a vibrating welding element. The vibrating welding element may be a horn vibrating at an ultrasonic frequency while it is brought into forced contact with one side of the overlapped webs while the other side of the overlapped web seam is supported on an anvil surface. Transfer of vibratory energy from the horn to the web material is effected upon impact of a suitably shaped surface of the horn on the seam of the web material. The vibrating energy causes surface heat to be generated between the overlapping webs along the area of contiguous contact between the webs. The horn normally resonates toward and away from the seam at a frequency of about 16 kHz or higher. The weld may be in the form of a chain of spots along the seam or a continuous weld. The technique of ultrasonic welding of thermoplastic material is well known and illustrated, for example, in U.S. Pat. No. 4,532,166, U.S. Pat. No. 3,879,256, U.S. Pat. No. 3,939,033, U.S. Pat. No. 3,947,307 and U.S. Pat. No. 3,459,610, all incorporated by reference herein in their entirety.
Unfortunately, batch processes for cutting and welding webs into belts require considerable time, duplicate manual handling, occupy excessive floor space and also require extensive equipment for alignment, cutting, welding trimming and other processing steps.
Further, excessive manual handling increases the likelihood of damage to sensitive substrates or coatings, particularly for coated substrates that must meet precise tolerance requirements such as flexible electrostatographic imaging members including photoreceptors for high speed electrostatographic copiers, duplicators, printers and the like. Scratches and even fingerprints on the vulnerable surfaces of a sensitive, flexible photoreceptor renders the photoreceptor unacceptable for most electrostatographic copiers, duplicators and printers.
In copending U.S. patent application Ser. No. 845,205 filed May 27, 1986 in the name of E. Swain et al, a process and apparatus are disclosed for fabricating belts in which a first cylindrical mandrel is conveyed to a wrapping station where the leading edge of a web from a web supply roll is supplied to the first cylindrical mandrel at the wrapping station. The leading edge on the first cylindrical mandrel is secured by means of a partial vacuum and the web is wrapped around the first cylindrical mandrel by rotating the first cylindrical mandrel for about one revolution. The web is then severed at the wrapping station to form a trailing edge which overlaps the leading edge of the web to form a first belt having a seam. The first mandrel is conveyed to a welding station and a second mandrel is substantially simultaneously conveyed to the wrapping station. The second mandrel is wrapped with fresh web material from the web supply roll and the seam on the first belt on the first mandrel is substantially simultaneously welded to form a unitary belt. These welded belts may be automatically removed from the mandrels at a belt discharge station. Although this approach produces excellent welded belts, the cylindrical mandrels are complex, heavy, and time consuming and expensive to fabricate. Due to the size and weight, considerable system down time is experienced while changing the three mandrels when a belt having a different circumference and/or width is to be fabricated. Moreover, the web pick up means is cumbersome, heavy, and expensive to fabricate. In addition, the seam of welded electrophotographic imaging members can only be prepared with the leading edge of the web underlying the trailing edge. The lap joint of a welded photoreceptor is normally conveyed in a direction which allows cleaning devices such as cleaning blades to ride smoothly over the lap joint much like rain is allowed to flow downwardly over lapped shingles on a roof. Electrically conductive ground strips are normally provided on only one edge of a photoreceptor. Some electrostatographic copiers, duplicators and printers require the ground strip to be along one edge whereas other electrostatographic imaging devices require the ground strip to be along the opposite edge. The use of cylindrical mandrel device in the above described copending patent application is also less versatile in providing welded photoreceptor belts for different electrostatographic copiers, duplicators and printers because, relative to the location of a ground strip, some imaging devices require lap joints having the leading edge of the web over the trailing edge whereas other imaging devices require lap joints having the trailing edge of the web over the leading edge.